The invention relates to a process and to an apparatus for the continuous hardening of pump casings which may or may not have an inner plating and with or without modifying the core characteristics by subjecting the inner surface of the casing to the action of a flame hardening apparatus.
Armoured pump casings are mainly made from cast steel. Wearing plates are not provided on the inside of such pump casings and repairs are carried out by welding the casing.
The casing for the pump system is constructed by fitting a cast casing into an outer sheet metal shell, which is split and whose two shell parts are screwed together. This casing is less expensive, because it does not have the otherwise necessary static ribbing and casing base. However, the prime costs for such pump systems are considerably higher.
In the case of large pumps, which are for example used in wet dredgers the inside of the pump casing is lined with wearing plates, i.e. internal plating is provided. Steel having a C-content of 0.12 to 0.8% is generally used for this purpose. The thickness of the wearing plates is dependent on the degree of wear and is laid down by the dredger companies, varying between 10 and 40 mm. As they are not hardened the hardness of the wearing plates is max. 20 MRC. In the case of one shift operation the internal plating has to be replaced two or three times yearly. However, as a function of the hydraulic packing material this figure may be increased or decreased.